Documentation of the cable plant is a necessary part of the design and installation process for a fiber optic network. Documenting the installation properly during the planning process will save time and material. It will speed the cable installation and testing since the routing and terminations are already known. After component installation, the documentation should be completed with loss test data for acceptance by the end-user. During troubleshooting, documentation eases tracing links and finding faults. Proper documentation is usually required for customer acceptance of the finished project.
The documentation process begins at the initiation of the project and continues through to completion. It must begin with the actual cable plant path or location. Outside plant cables require documentation on the overall route and details on exact locations, e.g., on which side of streets, which cable on poles, where and how deep buried cables and splice closures lay, and if markers or tracing tape is buried with the cable. Premises cables require similar details inside a building for the cable to be located anywhere in the path.
Most of this data can be kept in computer-aided design (CAD) drawings and a database or commercial software that stores component, connection and test data. Long outside plant links that include splices also may have optical time domain reflectometer (OTDR) traces, which should be stored as printouts and possibly in computer files for later viewing in the event that problems arise. Of course, that works only if a computer with proper software for viewing traces is available, so a copy of the viewing program should be on the disks. If the OTDR data is stored digitally, a listing of data files should be kept with the documentation to allow finding specific OTDR traces more easily.
The documentation process
Documentation begins with a basic layout for the network. A sketch on building blueprints may work for a small building, but a large campus, metropolitan or long-distance network will probably need a complete CAD layout. The best way to set up the data is to use a facility drawing and add the locations of all cables and connection points. Identify all the cables and racks or panels in closets. Then you are ready to transfer this data to a database.
Fiber optic cables, especially backbone cables, may contain many fibers that connect a number of different links, which may not all be going to the same place. The fiber optic cable plant, therefore, must be documented for cable location, the path of each fiber, interconnections and test results. You should record the specifications on every cable and fiber: the manufacturer, the type of cable and fiber, how many fibers, cable construction type, estimated length, and installation technique (buried, aerial, plenum, riser, etc.).
It will help to know what types of panels and hardware are being used and what end equipment (if any) is to be connected. If you are installing a big cable plant with many dark (unused) fibers, some will probably be left open at the panels, which also must be documented. When designing a network, it’s a good idea to have spare fibers and interconnection points in panels for future expansion, rerouting for repair or moving network equipment.
Documentation is more than records. All components should be labeled with color-coded permanent labels in accessible locations. Once a scheme of labeling fibers has been determined, each cable, accessible fiber and termination point requires some labeling for identification. A simple scheme is preferred and, if possible, explanations provided on patch panels or inside the cover of termination boxes.
Cable plant documentation records are very important. Keep several backup copies of each document, whether stored in a computer or on paper, in different locations for safekeeping. If a copy is presented to the customer, the installer should maintain his or her own records for future work on the project. One complete set on paper should be kept with a “restoration kit” of appropriate components, tools and directions in case of outages or cable damage. Documentation should be kept up-to-date to be useful, so that task should be assigned to one on-site person with instructions to inform all parties keeping copies of the records of updates needed. Access to modify records should be restricted to stop unauthorized changes to the documentation.
HAYES is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at www.JimHayes.com.